The invention disclosed herein relates to machines for applying labels to containers such as bottles. In particular, the invention pertains to devices for controlling the thickness of the film of glue on a glue roller which the labels contact to receive a coat of glue.
There are a variety of devices for applying glue to labels in preparation for applying the labels to bottles. A widely used type of device for applying the glue is described in U.S. Pat. No. 4,512,842. In the typical device, there is a turret rotating about a vertical axis. A series of curved glue pallets are arranged in a circle about the periphery of the turret. These segmental pallets oscillate about vertical axes. At one place in their orbit they contact a roller on whose periphery there is a film of glue. Upon further rotation, the pallets encounter a stack of labels in a magazine. The pallets press against the foremost level and rock so that a level is laid on the surface of the pallet. Upon further rotation, the pallet encounters the periphery of a transfer roller which picks off the labels from the pallet successively and applies the labels to bottles that are being conveyed through the labeling machine. In some cases, one label is applied to the cylindrical body of the bottle and another label is applied to the tapered neck portion of the bottle. Usually there is a doctor blade or the like in close proximity to the surface of the glue coated roller for scraping off all glue except for a thin film on the roller. It is necessary for the doctor blade edge to be perfectly parallel to the surface of the glue roller and it is necessary to provide for adjusting the glue scraping blade through a proper angle relative to the roller and with proper clearance to establish the desired film thickness.
In one known type of glue applicator device the scraper or doctor blade cooperating with the glue coated roller is adjustably arranged on a carrier by means of clamping screws and set screws. The carrier is mounted to a shaft and is rotatable about an axis which is parallel to the rotational axis of the glue roller and has an angular position which is adjustable by means of another adjusting screw as in DE-OS No. 15 86 370. The clamping and adjusting screws mentioned above permit the angular positioning of the scraper blade as well as the projection of the working edge of the blade over the side of the carrier. The adjusting screws acting on the carrier allow rapid and simple adjustment of the scraper blade to obtain the appropriate film thickness. At the basic set point, the working edge of the glue scraper or doctor blade is exactly parallel to the peripheral surface of the glue roller. In any case, glue film thickness on a roller must be precisely controlled. If the film is too thin, the labels will have a coat that is too thin and they may not stick to the bottles or other containers to which the labels are applied in the labeling machine. If the glue film on the roller is too thick, the film on the labels picked up from the label storage magazine will be too thick in which case the labels have a tendency to float or drift along the surface of the bottle to which they are applied. In another type of glue applicator device the glue scraper is arranged so as to be radially displaceable on a stationary carrier by means of clamping and adjusting screws, respectively, found in the lower and upper end area of the glue roller as in DE-AS No. 11 11 562. The angular position as well as the working edge clearance can be regulated with respect to the glue roller periphery by means of the adjusting screws. It is is necessary to correct or alter the thickness of the glue film which happens quite often during normal labeling machine operation, then it is particularly important to rotate both of the two adjusting screws uniformly or the scraper blade edge may not be parallel to the surface of the roller in which case the gap between the scraper edge and the roller will vary in thickness over the length of the roller.
In still another known glue applicator device provision is made for coating two different kinds of labels, one for the necks and another for the bodies of bottles. The adjustment of the glue strip for the body label takes place in the usual manner by means of an adjusting screw that determines its angular position while the adjustment of the glue scrapers for the neck labels scrapers is accomplished by means of eccentric bushings and adjusting screws.
If the glue scraper on one of the known gluing devices becomes unoperational as a result of damage or wear to its working edge, the glue scraper must be exchanged in one piece and the basic setting for the newly installed scraper must be adjusted precisely. The blade exchange procedure is time consuming and the cost of spare parts which must be kept on hand is considerable.